(471325) 2011 KT19

471325 Taowu (provisional designation , formerly nicknamed Niku ()) is a trans-Neptunian object whose orbit is tilted 110 ° with respect to the ecliptic. Thus, it has a nearly polar retrograde orbit around the Sun from the reference point of Earth's orbital plane.

Discovery

Taowu was discovered on 31 May 2011 by the Mount Lemmon Survey in Arizona. It was announced by the Minor Planet Center on 2 June 2011, after other telescopes confirmed the object with additional observations. The object was given the minor planet provisional designation , which reflects its discovery date. Initial calculations of Taowu's orbit using these few observations suggested it was a centaur on a prograde elliptical orbit (semi-major axis 28 AU, eccentricity 0.41, inclination 38°). However, Taowu was only observed for up to 8 days before being lost, due to large uncertainties in its orbit.

In 2016, a team of astronomers led by Ying-Tung Chen performed a search for outer Solar System objects in observations by the Pan-STARRS 1 survey. They rediscovered Taowu in Pan-STARRS observations from 2013–2016 and recognized it had an unusual retrograde polar orbit. Chen's team made follow-up observations at Lulin Observatory in Taiwan and found additional observations of the object in archival images from the Dark Energy Survey and Canada–France–Hawaii Telescope. After Chen's team submitted their observations of Taowu to the Minor Planet Center, it was recognized that Taowu had been previously observed by the Mount Lemmon Survey in 2011. Taowu received its permanent minor planet catalog number 471325 in 18 August 2016 and the Minor Planet Center declared Mount Lemmon Survey as the object's official discoverer.

Name

The object is named after Taowu, one of the Four Perils in Chinese mythology. The name follows the International Astronomical Union's naming conventions for centaurs on Neptune-crossing orbits (perihelion <30 AU), which are named after mythological chimeras. The name was announced by the International Astronomical Union on 3 February 2025.

The object was previously nicknamed "Niku" by Ying-Tung Chen, who was involved with rediscovering the object and studying its orbit in 2016. The nickname comes from the Chinese adjective meaning "rebellious", in reference to the object's unusual retrograde orbit.

Orbit

Taowu is in a 7:9 resonance with Neptune. Currently it is the only object with a nearly polar orbit that is in resonance with a planet. Notably, it is part of a group of objects that orbit the Sun in a highly inclined orbit; the reasons for this unusual orbit are unknown as of August 2016. Taowu's orbital characteristics have been compared to those of (nicknamed "Drac"). The orbits of Taowu, , , , , , appear to occupy a common plane, with three in prograde and three in retrograde orbits. The probability of this alignment occurring by chance is 0.016%. These orbits should leave a common plane in a few million years because the precession of prograde and retrograde orbits are in opposite directions. Simulations including the hypothetical Planet Nine did not maintain a common orbital plane and the plane does not coincide with the plane of the predicted high-inclination large semi-major axis objects of that model. Other simulations with a few Earth-mass dwarf planet on a high-inclination orbit also failed to reproduce the alignment.

Physical characteristics

The diameter of Taowu has not been measured, but it can be estimated from its brightness ( absolute magnitude) using a range of plausible values for its surface reflectivity (geometric albedo). If Taowu reflects between 5% and 25% of visible light, then its diameter is between . Taowu's rotation period had been measured as part of a 2023 study, but results have not yet been published.

References

External links

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{{DEFAULTSORT:471325
Trans-Neptunian objects
Centaurs (small Solar System bodies)
Taowu
Discoveries by MLS
20110531
Minor planets with a retrograde orbit